An exhausted 21-year-old Mormon, Gary, is on his way back to Lancaster from a two-year proselytising mission in Utah, and he summons the energy to try to rescue one more soul on the plane. At home, the boy's ailing mother has been forced to leave the house for the first time in two years; his brother, father and sister are all carrying shameful secrets; and they're all hoping that his return will put everything right.

This is the third novel from 30-year-old Jenn Ashworth, who grew up a Latter-day Saint in Preston, and it takes place during a single day, with each family member taking it in turns to narrate. While the plot gets increasingly outlandish as it hurtles towards its climax, many of the book's best moments describe quiet, humdrum events. Gary's inner monologue as he patiently turns a conversation with a salesman towards God, trying to ignore his own stammer, is a juicy glimpse behind the bland facade of evangelism. "I count, and breathe, and do my anxiety exercises. He is my brother. He is my brother. Brother. My brother."

The portrait of religion that emerges is nuanced. On the one hand, we get 14-year-old Jeannie being taught that her chastity is like icing on a cupcake – once one boy has licked it off, no one else is going to want the cake itself – with terrible consequences.

Pauline, who has been incontinent since Jeannie's birth, avoids medical help and places her trust in God, and Gary struggles with the expectations placed on him as a model Mormon. On the other hand, the close-knit community provides solace and there's a glimmer of authorial approval in Jeannie's observation that her immodest classmates "think they don't have anything to offer the world but their skin, their hair and their eyes".

Ashworth's style is matter of fact and full of detail: the pattern of a sofa, the shape of a meal tray, the cracks on a path. She's also unafraid of ugliness. Every bodily fluid imaginable makes a cameo at one point or another, and desire, when it appears, is almost always shameful, deluded, suppressed, cruel or just plain wrong. This often makes for grim reading, but Ashworth appears less interested in spreading a simple, comforting message than in uncovering the messy complexities of people, families and faith.